I would suggest the following:
- get a better charger. get one that will charge at the max rate the lipo can do.
- Confirm the settings on the ESC are correct for lipo usage
- If there is a punch setting, try turning that down and see how the performance is for stuttering. It may not be as snappy, but you can see if the battery is having trouble keepign up with the demand the motor is putting on it at that time. Some ESCs when you have a high punch setting will send all the power it can to the motor, which, if the battery can't keep up, will cause issues.